1. Field of the Invention:
This invention relates to a dynamic loudspeaker, and more particularly, to such a dynamic loudspeaker which may offset a reaction force generated by a diaphragm by a reaction force of a massive member being driven.
2. Description of the Prior Art:
Usually, a loudspeaker comprises a magnetic circuit formed by a magnet, a pole, a plate, and a yoke, a cone-shaped vibratory member having a voice coil disposed in an air gap of the magnetic circuit, and a support member for supporting the vibratory member, wherein the vibratory member vibrates in response to aural signals supplied to the voice coil. The loudspeaker is utilized by mechanically supporting the magnetic circuit and by securing a frame supporting the vibratory member to a baffle plate of a speaker box or an enclosure.
When the vibratory member of such loudspeaker is driven to vibrate in the forward or rearward direction, a reaction force acts in the rearward or forward direction to vibrate the magnetic circuit. Vibrations generated in the magnetic circuit will be transmitted to the baffle plate through the frame, thus the baffle plate will also vibrate. Vibrations of the magnetic circuit and the baffle plate have serious effects on tone quality of aural outputs generated by the vibratory member and deteriorate the tone quality of aural outputs.
For preventing vibrating of the magnetic circuit and the like caused by reaction force generated in driving the vibratory member, it is known to sufficiently increase the weight of the magnetic circuit and the like as compared with that of the vibratory member and the voice coil, however, when the weight of magnetic circuit and the like is increased to substantially overcome the reaction force, there are problems in practical use such as difficulties in assembling or transporting the loudspeaker which is not preferable for the construction of loudspeakers of the usual type. Further, the baffle board or the enclosure mounting the speaker is usually formed of a high quality material to prevent vibrations thereof, thus, the enclosure is expensive.
In a speaker system comprising a vibratory member of a first speaker being disposed in an opening of the enclosure, and a second speaker disposed opposingly with the first speaker and in the enclosure, reaction force of the first speaker can be absorbed by the second speaker. However, acoustic pressure from the second speaker will act on the enclosure in such speaker system, even though it is possible to suppress vibrations in magnetic circuit of the first speaker, vibrations will occur in the enclosure, and acoustic waves generated from the first speaker will interfere with acoustic waves generated from vibrations of the enclosure, as the results, it is difficult to obtain clear play back sounds.